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Engine running hot TD42???

550K views 3K replies 251 participants last post by  C.Chris 
#1 · (Edited)
spent hundreds if not thousands trying to stop it running hot ???

well i have the answer for you and it is fairly cheap , no need for multi pass alloy radiators or anything like that , although i do recommend that all cooling system componants be in good running order

this fix is for most if not all bypass type thermostats ie: looks like this ( specs will vary)



how the bypass thermostat works is ... that it will allow coolant to recirculate through the motor without having to go through the radiator as well as allowing coolant through the radiator

what i have found is that the bypass valve isnt blocking the flow of coolant that gets recirculated through the motor ( bypassing the radiator ) soon enough, basicly the thermostat has to open alot further before stopping this recirculation bypassing the radiator, this may mean the coolant temp has to reach around 100 deg or more before all the coolant has to go through the radiator

now the above pic shows some specs

54mm is the thermostat flange diameter

35mm is the closed thermostat hight between the flange and the bypass blocking plate

the 27.7 mm is the blocking plates diameter

now on my car the distance between where the thermostat flange sits and the surface where the bypass valve/ plate is to sit is 40mm , this means my thermostat would have to open 5mm before it will block the flow of coolant that bypasses the radiator, and in my case this means the coolant has to reach over 100 deg

what i have done is increased the closed thermostat hight between the flange and the bypass blocking plate to 38 mm , this means the thermostat now only has to open 2mm before all coolant has to travel through the radiator and the coolant temp is only around 90 deg at this stage

the results are impessive to me , i can tow my camper trailer up a mountain range with the temps maxing out at around 92 deg , i only have a falcon thermofan set up with the fans set to turn on at around 90 deg ( about 1/2 way on my factory guage) , and they easily kept up with cooling , hwy driving saw the temp guage sit around 1/3 and not needing the thermo fans at all to keep it cool

what i recommend to people who are having a hot running issue is to take some measurements to see how far your thermostat has to open before the blocking plate/ bypass valve makes contact with its intended seated surface, if it is 4mm or more then this mod is for you, reducing the closed thermostat gap to about 2mm should mean all the coolant will be traveling through your radiator by the time the coolant reaches about 90 deg, instead of recirculating hot coolant through the motor

this mod should allow coolant to recirculate and bypass the radiator when the motor is cold and force more coolant through the radiator once the motor is at running temp

any questions just ask away and i will try to answer them the best i can

Posted from the thread, So it is easy to find this data.

updates?

anyone else done this?
reviews and what not?

IAFNAN, would this help my case?

currently, temp gauge hardly moves a needle width about C on the gauge,
im guessing my thermostat is farked and locked wide open..

you prob have done this over and over..
but can you explain it so a dummy can understand?

i have no idea what temp it currently runs, i should hook up my mechanical temp gauge.

my factory gauge tends to move with the speed i do..

0 - 60kph the needle sits below the C line.
60 - 80kph the needle sits on the C line.
80 - 100kph the needle sits above the C line.

or do i just go to my mechanic and have him put in a 82 degree thermostat and see what that does first?

any imput would be appreciated.

from what you have posted it looks like your thermostat is stuck wide open, and as you are not having any heating issues as yet i would just replace with a new thermostat, tridons TT228-180 is an 82 deg thermostat for the later model td42 and should work fine, or there is the high flow version TT2028-180 which is the same specs just high flow, both of these are just a strait put in and forget no mods needed.

the only uncertainty is how well the standard thermostat will cope under high load and/or heat situations, this is where (if your temps are fluctuating wildly) i recommend fitting a different thermostat or modding your standard thermostat so it can control the coolant temp better, now a factory thermostat which has the following specs



has to open up 9mm before closing the bypass hole so all the coolant flows through the radiator (ie: the 31mm distance in the diagram has to open up to 40mm to close the bypass hole), this is why alot of people have hot running issues with there TD42`s as the coolant temp has to rise about 20 deg before the bypass hole closes and the temp guage is all over the shop when the car looks at a hill.

the easiest thermostat to fit (no mods) is what i recommended to you first up "TT228-180 or TT2028-180" specs are

and is an improvement over the factory spec thermostat as they will control coolant temps a bit better because they only have to open 5mm before blocking the bypass hole, (the bypass hole is 40mm below the flange of the thermostat) , but even this thermostat allows the coolant temps to fluctuate a bit although not as bad as the factory thermostat

this is where i got a different thermostat again (couldnt find one with the specs i wanted so i had to get one and moddify it) the only one i could find close enough to suit my needs with minimal mods needed was a dayco DT79H which has the following specs

now this thermostat has a 41mm distance from the flange to the bypass blocking plate, if i fitted it strait in it would mean the bypass hole is always blocked which is not what you want, you need to change the 41mm distance to about 37-38mm so when the motor is cold the coolant will still circulate through the motor, basicly you need to space the bypass blocking plate up about 3 to 4mm

the DT79a rated at 82deg
http://www.eziautoparts.com.au/dayco-thermostat-dt79a.html
the DT79h rated at 85deg
http://www.eziautoparts.com.au/dayco-thermostat-dt79h.html
the DT80g rated at 89deg
http://www.eziautoparts.com.au/dayco-thermostat-dt80g.html


the other option is to weld in an alloy washer/ring on top of the bypass hole to reduce the distance the thermostat has to open before blocking the bypass hole, this way you could still use the factory thermostat and have better control of the coolant
 
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#1,997 ·
Sustain the load long enough and temp will increase. It's 10•c past thermostat temp
So ten degrees variance is not stable you say . So when I had stock fan and hub and thermostat it would be a lot more than 10 degrees difference . So stock is no good . Using after market is no good . What is stable and a acceptable variation in temp ??? I know you love to talk about water pumps but thousands of people are getting great results without touching the water pump . Very few people Touch the water pump . Radiator. Thermostat. And fan and hub .and new coolant . seems to be the most popular and successful way to get outstanding results .
 
#1,992 ·
Well this is getting a bit complex here with so many view points.
- First of all the thermostat is not the main problem with the TD Our water pump is the problem "Period". The correct thermostat mod outlined here is to adjust the bypass flap so its 3mm or so off the bypass at ambient. So on a DT79A we shim the flap up 3mm to 4mm or so off the seat. This allows the water to bypass when the thermostat is closed. If the bypass is blocked your pump will not flow water in preheat phase. The pump will cavatate making things worse. The idea is to allow water to flow through the bypass until the thermostat opens so we get some sort of effective preheat in the engine and reduce pump cavatation and allow the pump to flow. Our pump will not flow water if the bypass is closed and the thermostat valve is closed. Our pump has near zero pressure at idle and about 3 psi at 2400 rpm temp expansion aside with the thermostat fully open. For pressures measured at the low pressure side of the Radiator it is usual to measure-:
Stock: 14-18PSI
High performance: 22-24 PSI
Racing: 29-31 PSI For a good cooling system at cruise speeds, our TD is way below the normal pressure needed. Hence our problem period any thing else we do is a band-aid fix.

-Secondly i will say this again with lots of emphasis, "There is no such thing as too fast a water flow in a closed loop radiator system" Reason water by its nature will drop 15 to 25 degrees depending on radiator design and whether you have alloy or copper brass near instantly. To drop temps further for the same volume flow you need a better cooling agent than ambient AIR. Or a radiator exponentially larger in fin area and tube area to allow the surface exposure flow to lower the out bound temps to be closer to ambient air temps. It's not the top down temp or the time in the radiator that controls temps out the radiator its the ambient airs ability to remove the temps at a given air speed past the fins and internal surface area not bloody time thats a Myth, because "time spent in the rad" is not a defining factor of how well a rad cools, and that flow, turbulence, and delta-T have a far greater effect on cooling efficiency than time. In addition, there are a great many aspects of radiator design, including tube width, tube height, number of tubes, tube construction, and fin count that, in addition to flow pattern, all combine to determine the cooling efficiency of a radiator. More time spent in a radiator is pressure drop hence less flow. More flow means more cooling to the engine or more precisely more stability.

-Thirdly our radiator size. As a general rule we use a ratio of 1.2 sq inch / hp for a good alloy radiator size with a steel block. So for a GQ radiator 29x18 inch that enough for 435 hp at the engine so about 360 hp at the wheels. For a brass/copper you want to be using 1.4 sq inch / hp so for a GQ that 370 Hp engine and 300 hp at the wheels. For an alloy radiator and alloy block you would use 1.1 sq inch / Hp. So you see our Radiator is big enough to do the job but we just do not have enough flow through the system to have stability.
 
#1,995 ·
Well this is getting a bit complex here with so many view points.
- First of all the thermostat is not the main problem with the TD Our water pump is the problem "Period". The correct thermostat mod outlined here is to adjust the bypass flap so its 3mm or so off the bypass at ambient. So on a DT79A we shim the flap up 3mm to 4mm or so off the seat. This allows the water to bypass when the thermostat is closed. If the bypass is blocked your pump will not flow water in preheat phase. The pump will cavatate making things worse. The idea is to allow water to flow through the bypass until the thermostat opens so we get some sort of effective preheat in the engine and reduce pump cavatation and allow the pump to flow. Our pump will not flow water if the bypass is closed and the thermostat valve is closed. Our pump has near zero pressure at idle and about 3 psi at 2400 rpm temp expansion aside with the thermostat fully open. For pressures measured at the low pressure side of the Radiator it is usual to measure-:
Stock: 14-18PSI
High performance: 22-24 PSI
Racing: 29-31 PSI For a good cooling system at cruise speeds, our TD is way below the normal pressure needed. Hence our problem period any thing else we do is a band-aid fix.

-Secondly i will say this again with lots of emphasis, "There is no such thing as too fast a water flow in a closed loop radiator system" Reason water by its nature will drop 15 to 25 degrees depending on radiator design and whether you have alloy or copper brass near instantly. To drop temps further for the same volume flow you need a better cooling agent than ambient AIR. Or a radiator exponentially larger in fin area and tube area to allow the surface exposure flow to lower the out bound temps to be closer to ambient air temps. It's not the top down temp or the time in the radiator that controls temps out the radiator its the ambient airs ability to remove the temps at a given air speed past the fins and internal surface area not bloody time thats a Myth, because "time spent in the rad" is not a defining factor of how well a rad cools, and that flow, turbulence, and delta-T have a far greater effect on cooling efficiency than time. In addition, there are a great many aspects of radiator design, including tube width, tube height, number of tubes, tube construction, and fin count that, in addition to flow pattern, all combine to determine the cooling efficiency of a radiator. More time spent in a radiator is pressure drop hence less flow. More flow means more cooling to the engine or more precisely more stability.

-Thirdly our radiator size. As a general rule we use a ratio of 1.2 sq inch / hp for a good alloy radiator size with a steel block. So for a GQ radiator 29x18 inch that enough for 435 hp at the engine so about 360 hp at the wheels. For a brass/copper you want to be using 1.4 sq inch / hp so for a GQ that 370 Hp engine and 300 hp at the wheels. For an alloy radiator and alloy block you would use 1.1 sq inch / Hp. So you see our Radiator is big enough to do the job but we just do not have enough flow through the system to have stability.
As of a week ago we now have the advance search function back which makes it much easier to find posts from certain members. You can't search specific threads but you can narrow it down to the specific forum section and exact members only.

Either that or you could also ignore certain members and then none of their annoying posts will be cluttering the thread you are trying to read. Just move the mouse over their username and click the ignore button. Refresh the page and like magic all their posts are gone! :LOL:

In the period of us not having an advanced search function I've at times ignored everybody except the one person I wanted to read posts from and it was brilliant.
That is brilliant.
Will save a lot of misinformation!

Edit- sorry Pete not sure why it quoted you as well.
 
#1,994 ·
As of a week ago we now have the advance search function back which makes it much easier to find posts from certain members. You can't search specific threads but you can narrow it down to the specific forum section and exact members only.

Either that or you could also ignore certain members and then none of their annoying posts will be cluttering the thread you are trying to read. Just move the mouse over their username and click the ignore button. Refresh the page and like magic all their posts are gone! :LOL:

In the period of us not having an advanced search function I've at times ignored everybody except the one person I wanted to read posts from and it was brilliant.
 
#1,998 ·
Have a look at post #1992 mate.
OldMav knows his shlt.
He has written previously about the std pressed metal impeller having too much clearance to the pump housing from factory.
If he is saying it is so, then I believe it [emoji6]
Plumma has measured the pressure the pump produces I believe.
 
#2,003 ·
A copy paste from some writings from a thermodynamics Engineer from Griffin Radiators in the US. Not my words but from a different source to dispel these flow Myths and old thoughts.


"My recommendation is to always use a thermostat. The reason is simple - its job is to regulate operating temperatures so that the engine warms up as quickly as possible, and then remains at the designed operating temperature. Without a thermostat, the engine may take far too long to warm up, and in some conditions may not warm up properly at all. When the engine is below operating temperature the oil's viscosity is too high to properly lubricate the engine, particularly the critical bearing clearances. Combustion efficiency (and therefore power production), emissions, and component wear also suffer.

One thing to be careful of though, when designing your system and using a thermostat, is to ensure your water pump has an internal bypass circuit (refer back to #6 in the flow diagrams above). Most do, but some aftermarket high-flow racing pumps do not. For these pumps, a special thermostat with a bypass hole is used, or the user drills their own bypass holes in the thermostat (typically one to three 3/16" holes) so that the system can flow when the thermostat is closed.

If you choose to run without a thermostat, do not use a restrictor. The restrictor will do nothing for you except reduce coolant flow which ultimately reduces cooling.

Years ago restrictors were popular for two reasons that do not hold true today. First, as we have discussed, older radiator designs (large cross-sectional area copper tubes) were poor at promoting the necessary coolant turbulence in the radiator, so a restrictor was used to cause the coolant to begin tumbling as it exited the engine and entered the radiator. Secondly, with engines that had the thermostat located in the outlet of the engine combined with down-flow radiators that had a fairly low pressure radiator cap on the high pressure inlet side, if the thermostat was removed the increased pressure seen by the cap from the water pump could cause the cap's rating to be exceeded and the valve to open and purge coolant. Since this opening of the rad cap is what regulates system pressure, it meant that the overall system pressure would now be lower - the cap would open sooner than if the thermostat were in place holding backpressure in the cylinder head. Since system pressure was now lower, coolant vapour point was lower, and therefore the coolant's ability to effectively carry-off heat from the engine at higher temps reduced. This in turn would result in eventual overheating. Many folks erroneously assumed that the overheating was due to the coolant flowing through the radiator too quickly with the thermostat removed, that it didn't have time to cool in the rad. As a result, restrictors were used to "slow the flow of the coolant" and the car stopped overheating. Unfortunately, these folks didn't understand the real cause and effect of the overheating that they experienced after removing the thermostat, and this led to two enduring myths that persist today.

What was really happening was that the removal of the thermostat didn't cause the coolant to flow too fast to cool (we know this is an impossibility), but rather caused a condition where either system pressure (and therefore coolant vapour point) was lowered or where the rad purged coolant which caused the car to overheat. The end result was the same - the car overheated - but the cause and effect were confused and so the myths that a) removing a thermostat can cause a car to overheat and b) coolant can be pumped too fast through a radiator to cool properly began. Neither of these are true.

Of course, today's cross-flow radiators that locate the rad cap on the low-pressure side, do not subject the rad cap to the maximum pressure created by the water pump and so are not susceptible to the pump forcing coolant past the rad cap. We also know now that all systems benefit from maximum flow - never from reducing flow.

Ultimately, reducers reduce the flow of coolant which actually hurts system cooling efficiency, not improves it."
 
#2,013 ·
Plumma's system is not a controlled bypass with and by the thermostat its a permanent bypass all the time. The thermostat only allows water to the radiator when needed controlled by the thermostat. This type of system only works with high flow and pressures. The water hardly slows down when the thermostat opens due to the higher volumes and other bits in the system to have the same head pressures in the system regardless of thermostat open or closed, so the pump will only even see the same head regardless of closed or open thermostat so the same volume flow regardless of the thermostat open or closed.

The volumes being shifted are quite a lot so cooling is quite a lot. With these volumes and flow values its very easy to over cool. The laws of thermodynamics are still at play here, hot water hitting the radiator regardless of volume will still release 15 to 25 degrees C near instantly. But due to the way better water control and speed in the block using all the water to stabilise temps with the thermostat cycling open and closed all the time at its preset temp water stays in the radiator longer for a few more degrees of cooling dependent on engine loading and heat generation to have more effective block/head stability control with loading.

Even in the block more water flow equals more cooling, in the head where most of the heat is generated the high flowing water keeps those insulating bubbles at bay for better heat transfer and the water speed uses more of the water through the head to absorb heat which has less differential temps between block and head for more stability and cooling. This sort of cooling stability will keep all our cylinders at equal temps so the combustion burn temps are similar for more even combustion loading on each cylinder unlike our std system allowing temps in 5 and 6 cylinders to be a lot higher causing different cylinder loading's..

For diesel we have better power/torque when water temps are at or a bit above 90 C and stable. Many marine engines are at 96C to gain this extra free power values and economy. But marine engines have 24ish degrees C of near infinite water supply to control temps.
 
#2,014 ·
I notice some people are fixated on the water pump ? My question is why are 99 % of over heating issues solved with a new radiator same size as genuine plus a thermostat and occasional a upgraded fan and hub ? I hear of very few people touching the water pump and bragging of good results . Yet I hear everyday of great and no more over heating with the other option .
 
#2,015 ·
My question is why are 99 % of over heating issues solved with a new radiator same size as genuine plus a thermostat
I'd say you are dead wrong with that comment which is why this thread exists.I went from a stock radiator that would often cause issues while towing to an expensive three row copper brass unit and gained an improvement but still suffered from overheating when towing the caravan in temps mid thirties or above in hilly terrain. Thermostat change made no difference at all. All the people I've talked to that have messed with the water pump have done it because they still had problems after better radiator, thermostat and fan still left their car with temp issues.
 
#2,016 ·
I can only go by what I read and talk to others and I cant say I know to many people that have changed the water pump and has the over heat issue disappear . Even some diesel/shop tuners . Never touch the water pump and get great results . Maybe ask your self how many people have changed water pumps or many have gone down the other route . And ask people not just on here ? Water pump sales must be booming ?
 
#2,018 ·
JPC sells alot of td42 water pumps.
I've seen the boxes of cnc impeller being made.
It seems like a last resort for those that have run out of patience.
These custom pumps are far from cheap and having spoken to JPC are untested as well. They just assume a shiny brass impeller must work.
Sorry to be the bearer of bad news....
It doesn't.
I believe I can accurately say that I am probably the only person to fully test and diagnose the cooling system faults of a td42. And yes I did research it extensively before I started to try and short cut the process.
With the water pump we developed it had a couple of design criteria.
Firstly, it must fit any td42 without any mods to the engine. A simple bolt on pump is what is needed.
Secondly, pump MUST NOT cavitate.
Thirdly, pump MUST make pressure.
certain pressures were required at idle through to WOT.
Fourthly, good flow must be also achieved.

This just wasn't achieved overnight by simply changing impeller design.
It was a timely process where each single pump change was tested.

I now have a water pump that could bolt to any unmodified td42 timing case cover and work along with the other cooling mods that support the pump.
 
#2,017 ·
I don't think there is any single cure-all for for a TD42 heat problem but the best results I've seen are from getting more air through the radiator regardless of the method that is used to achieve that. I've known very few people that have put a better water pump on but those that have done so have had a substantial improvement from it however they have already done a bunch of other stuff to improve their cooling system. I don't think for a moment that a water pump change by itself will fix anything.
 
#2,022 ·
There are still some things about the cooling system mods that need tweaking. Plans were to be finished before Xmas but at this stage with that about 10 weeks away I can't see that happening. Hopefully the last mods should be easy as the time consuming parts completed.
 
#2,028 · (Edited)
Well about 24 hours and I have one person that has purchased a jpc water pump . So imo not really In high demand for these ?
Over on the TD42 Facebook page you see them get mentioned on a fairly regular bases with quite a few guys saying they are running them.

Which means due to the way Facebook works, they'd sell like hotcakes! Only takes one post to be seen buy a bunch of young blokes who tag all there mates and they all run off and throw money at the latest fancy shiny upgrade part they discovered. Then the next week when someone posts about it again a whole new group of blokes see it and the cycle continues. Just the way the world works now, if you want to sell a product get people posting it on Facebook 👌
 
#2,039 ·
Engine is running the TD42 sensor that is connected to the factory TD42 ECU. The 98 had a 2.8 dash and the 05 has the 3l dash. As far as the coolant plumbing goes it is the same as it would be factory, except at the moment I am just running a recovery tank instead of the header tank set up. I tried both with and without a header tank on the 98 , and it made no difference. Currently has an Adrad factory radiator.
 
#2,041 ·
I hadn't bothered repeating myself here but a mate (real and close not Fakebook or made up) did everything with air dams, factory style radiator, factory ally bullbar, ufi fan and hub. All made a very small improvement but the jpc pump in his case made the most difference. Not perfect but well good enough to allow him to head off on a lap towing a 17 foot van.
He hasn't been on here for a couple years now hence didnt respond
 
#2,045 ·
Hmmm, so sort of in between the Patrolapart and JPC design. I wonder what the "testing" is.
 
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